1 Overview Importing data from generic raster files Creating surfaces from point samples Mapping...

1

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal Statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

2

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

3

Importing data from generic raster files

• ArcGIS can import grids from 4 different generic raster data formats– ASCII raster file format– binary raster file format– USGS Digital Elevation Model (DEM) raster

file format*– US DMA (Defense Mapping Agency) DTED

(Digital Terrain Elevation Data) raster file format

* common format; free for download from USGS

4

Importing data from generic raster files

• USGS DEMs are available online (free)

USGS source

5

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

6

Creating surfaces from point samples

• Generation of a complete surface from incomplete point samples

• Interpolation between and beyond individual sample points

• Better estimation of surface value in locations near sample points

• Several different interpolation methods available• Assumption of gradual change of value across

landscape

7

Creating surfaces from point samples• Points are interpolated to a surface Contin

uous surface

discrete sample points

8

Creating surfaces from point samples

• Two basic methods (spline and IDW)

• spline (minimized curvature)

• inverse distance weighting (local influence is strong)

9

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources_

10

Mapping contours

• Finds adjacent cells of the same value

• Converts linear arrangement of raster cells to vector lines

• User control of base contour and contour interval

• Few digitized contour line data sets exist for remote areas

11

Mapping contours

• Group of contours created as shapefilenew layer

12

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

13

• Defines a zone of cells based on a group of integer cells or polygons with same value

• Creates statistical summary of zone

• Summary table is created

• Summary chart

Summarizing zones

14

• “Zone” is a group of cells (or polygons) that have the same attribute value

Summarizing zones

15

• Table and chart are created

statistics from input grid based on polygonal zones

Summarizing zones

16

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

17

Cross tabulating areas• Creates a “zonal intersection” of integer grid

layers (similar to vector intersection)

• Output is a table

• 1st input layer creates records (1 record for each unique value)

• 2nd input layer creates fields (1 field for each unique value)

• Table values are map unit area measurements of combinations of zones

• Valuable technique for change detection

18

Cross tabulating areas• Output table

row

laye

r (s

oils

)

column layer (stands)

area measurementsin map units

19

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

20

"Querying" across multiple grid layers (“Map Query”)

• Raster Calculator is easy to use and gives rapid results

• Results may be as good as vector overlay depending on cell size & relative precision

• Multiple grids can be simultaneously queried(whereas only 2 vector layers can be compared in vector overlay)

• Output represents cells that meet and do not meet query criteria

21

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

22

Calculating neighborhood statistics

• “Focal” statistical functions

• Moving focus window calculates statistics for all cells within focus

• Output value is written to central cell in output grid

• Statistical functions:• Minimum• Maximum• Mean• Median• Sum

• Range• Standard Deviation• Majority• Minority• Variety

23

Calculating neighborhood statistics

• Focal Standard Deviationlocations of greatest variationin elevation

24

Calculating neighborhood statistics: high pass filter

• High-pass filter (focal process)

25

Calculating neighborhood statistics: high pass filter

• High-pass filter finds edges edges are higher or in absolute value

26

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

27

Calculating distance surfaces and buffers

• Similar to buffering with vector data

• Creates a continuous distance surfacerather than a discrete bounded polygonal area

• Distance measured from input layer featuresor grid cells

28

Calculating distance surfaces and buffers

• Distance from vector features

continuous distance value surface

29

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

30

Assigning proximity• “what territories are closest to a set of

features?” • output cells have the value of the closest input feature

“Thiessen,” “Voronoi”

31

Overview• Importing data from generic raster files• Creating surfaces from point samples• Mapping contours• Calculating summary attributes for polygon

features using a grid layer (“Zonal statistics”)• Cross tabulating areas• "Querying" across multiple grid layers• Calculating neighborhood statistics• Calculating distance surfaces and buffers• Determining proximity• Converting raster and vector data sources

32

Converting raster and vector data sources

• Raster vector conversions are possible

• Always a loss or generalization of shape

• Support for point, line, polygon grid in ArcGIS

• Avoid converting grids that do not have large contiguous zones (e.g., DEMs)

33

Converting raster and vector data sources: grid to polygon

• Convert grid zones to polygon shapefilepolygon shapefile

34

Converting raster and vector data sources: grid to polygon

• Convert grid zones to polygon shapefileGRIDCODEfield

35

Converting raster and vector data sources: grid to polygon

• Convert vector lines to grid zones

Value field